This invention relates to a drill jig, and particularly to a drill jig for use in preparing a door to receive a cylindrical lockset provided with through-bolt mounting studs.
Locksets intended for installation in a door are commonly packaged with hardware, instructions, and one or more templates to aid in the drilling of holes and other installation steps.
Generally, the templates were made of paper. There are several problems associated with the use of paper templates. Paper templates crease and tear thus making them difficult to use. The fragility of paper templates also renders them unsuitable for repeated use. Paper templates only provide marking points for the mounting holes, but still allow improper alignment, perpendicularity, or sizing of mounting holes. This inaccurate door preparation can allow excessive chassis rotation and drooping or sagging lever handles, and occasionally can inhibit proper lockset function.
The drill jig of this invention is designed to overcome the problems associated with such previous paper templates. The jig can be easily and economically manufactured from materials which retain adequate strength and shape for subsequent use. The drill jig of the present invention was developed to ensure proper hole size and to accurately align and drill mounting holes during door preparation for a through-bolt type of door trim.
According to the present invention, a drill jig is provided for preparing a door to receive a lockset provided with through-bolt or anti-rotation studs. The drill jig comprises a planar body having a front surface and a back surface joined by a perimetral edge. The planar body has at least two fixed metal bushings. Each metal bushing includes an aperture sized to receive a drill bit therein. The front surface has a portion for receiving a C-clamp to hold the drill jig in a fixed position in a door and a portion for displaying printed installation instructions. The perimetral edge includes a linear vertical portion for squaring with an edge of the door. The metal bushings of the jig provide adequate guidance and support for the drill bit to prevent improperly aligned, placed, or sized mounting holes.
A cylindrical body is appended to the planar body and oriented to extend in a perpendicular direction away from the back surface of the planar body. The cylindrical body has a latch slot that is sized to receive a latch therein to provide proper alignment and location of the mounting holes with respect to the lock chassis and to prevent rotation of the drill jig while drilling the mounting holes. The latch slot has chamfered edges that face the latch back plate and engage the latch plate to prevent rotation of the jig which might otherwise happen as the mounting holes are being drilled. The cylindrical body includes additional slots for flexing to ensure that the chamfered edges of the latch slot firmly engage the latch back plate. The cylindrical body also includes a tab for flexing to ensure a tight fit into the main bore of the door.
Preferably, the drill jig is injection-molded or otherwise formed of plastic. A plastic jig has the advantage of being manufactured easily and economically by injection-molding. Unlike paper templates, such a plastic jig retains adequate strength and shape for repeated use. The metal bushings provide strength and support to prevent the rotating drill bit from wandering off-center and from causing oversized mounting holes.
In a preferred embodiment, the frontal area of the jig is large enough to allow the attachment of a C-clamp, eliminating the need to hold the jig manually while drilling. This feature has the advantage of providing a frontal area for the jig which is also large enough to allow the placement of molded-in installation instructions, eliminating the need for printed paper instructions. A linear vertical portion of the jig also allows the jig to be squared with an edge of the door if a latch is not available or installed.
Additional features and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.